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It has been certified that MAYANK CHAUDHARY , Studying in XII A(Science), during the academic year 2016-17 has completed a project on “the study of effect of metal coupling on the rusting of iron” and has given a satisfactory account of this in their project report

(Chemistry Teacher)


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I MAYANK CHAUDHARY of Class XII A (Science), JKG INTERNATIONAL SCHOOL Indirapuram, declare that the following project on “the study of the effect of metal coupling on the rusting of iron” has been accomplished under the able guidance of our Chemistry Teacher, Ms DEEPA ADHIKARI ofJKG INTERNATIONAL SCHOOL Indirapuram , Ghaziabad

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I would like to express our sincere gratitude to Ms DEEPA ADHIKARI mam , our chemistry teacher, whose help and encouragement made this project possible. I would also like to thank Ms JHARNA mam , the lab Assistant for her help during the completion of this project. XII A (Science) JKG INTERNATIONAL SCHOOL Indirapuram , Ghaziabad

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Introduction Mechanism of corrosion of meta Electrochemical Mechanism(rusting) Methods of Prevention of Corrosion Aim of this project Requirements Procedure Observation Conclusion Bibliography

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Metal corrosion is the most common form of corrosion. The corrosion occurs at the surface of the metal in forms of chemical or electrochemical reactions. This process significantly reduces the strength, plasticity, toughness and other mechanical properties of the metallic material. However, because of the metal and its alloys is still the most important pipe and structure materials, the cost of corrosion grows significantly with the growth of industries. Thus many scientists focus on the research of corrosion control in order to reduce the cost of replacing the rusting metal material. Nowadays, there are mainly

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two corrosion control methods that are very popular in the world. One is impressed current and another is sacrificial anode cathode protection system. In this project, we will focus on the mechanism and application of the sacrificial anode cathode protection system.

Mechanism of corrosion of metal

General Principle of Corrosion:

Reaction is the fundamental reaction during the corrosion process, which the electron can flow from certain areas on the metal surface to other areas through a solution which can conduct electric currents.

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Basically, both anodic and cathode reactions have to balance each other out, resulting in a neutral reaction. Both anodic and cathodic reactions occur simultaneously at the same rates. What’s more, the site of these electrodes may consist of either two different kinds of metals, or they may

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be on different areas of the same piece of metal, resulting a potential difference between the two electrodes, so that the oxidation reaction of the metal at the anode and formation of negative ions at the cathode can take place at the same time.

Similar electrical potentials may also be developed between two areas of a component made of a single metal as

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result of small differences in composition or structure or of differences in the conditions to which the metal surface is exposed. That part of a metal which becomes the corroding area is called the “anode” ; that which acts as the other electrode of the battery is called “cathode” which does not corrode, but is an important part of the system. In the corrosion systems commonly involved, with water containing some salts in solution as the electrolyte.Corrosion may even take place with pure water, provided that oxygen is present. In such cases oxygen combines with the hydrogen generated at the cathode, removes. Rusting: an Electrochemical Mechanism

Rusting may be explained by an electrochemical mechanism. In the presence of moist air containing dissolved oxygen or carbon dioxide, the commercial iron behave as if composed of small electrical cells. At anode of cell, iron passes into solution as ferrous ions. The electron moves towards the cathode and form hydroxyl ions. Under the influence of dissolved oxygen the ferrous ions and hydroxyl ions interact

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to form, i.e., hydrated ferric oxide.

Methods of Prevention of Corrosion and Rusting

Some of the methods used:-

1) Barrier Protection: In this method, a barrier film is introduced between

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iron surface and atmospheric air. The film is obtained by painting, varnishing etc.

2) Galvanization: The metallic iron is covered by a layer of more reactive metal such as zinc. The active metal The active metal losses electrons in preference of iron.

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In this project the aim is to investigate effect of the metals coupling on the rusting of iron. Metal coupling affects the rusting of iron. If the nail is coupled with a more electro-positive metal like zinc, magnesium or aluminium rusting is prevented but if on the other hand, it is coupled with less electro –positive metals like copper, the rusting is facilitated.

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1) Two Petri dishes 2) Four test-tube 3) Four iron nails 4) Beaker 5) Sand paper 6) Wire gauge 7) Gelatin 8) Copper, Zinc and Magnesium strips 9) Potassium ferricyanide solutions 10) Phenolphthalein

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PROCEDURE 1) At first we have to clean the surface of iron nails with the help of sand paper. 2) After that we have to wind zinc strip around one nail, a clean copper wire around the second and clean magnesium strip around the third nail. Then to put all these three and a fourth nail in Petri dishes so that they are not in contact with each other.

3) Then to fill the Petri dishes with hot agar agar solution in such a way that only lower half of the nails are covered with the liquids

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4) Keep the covered Petri dishes for one day or so.

5) The liquids set to a gel on cooling. Two types of patches are observed around the rusted nail, one is blue and the other pink. Blue patch is due to the formation of potassium ferro-ferricyanide where pink patch is due to the formation of hydroxyl ions which turns colorless phenolphthalein to pink.

S. No Metal Pair Colour of the Patch

Nails rust or not

1 Iron-Zinc

2 Iron-Magnesium

3 Iron-Copper

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It is clear from the observation that coupling of iron with more electropositive metals such as zinc and magnesium resists corrosion and rusting of iron. Coupling of iron with less electropositive metals such as copper increases rusting.

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For our project I have taken help from following sources;

1) Comprehensive (practical Chemistry-XII) 2) Internet- 3) NCERT Chemistry Textbooks 4)